The known method of separation of granular mixture in a flowing medium consists of gravitational supply of the mixture particles into a separation zone, in an aerodynamic monotonically increasing impact on them at an acute angle to the vertical by the cascade of flat air jets and extraction of finished fractions. Such an aerodynamic impact is carried out in the regime of free alternating power scanning with increasing scanning amplitude and scanning angle. The device for carrying out such method of separation of granular mixture comprises a hopper with a vibrating chute, and the installed under it generator of air jets with flat nozzles arranged one under another and at an acute angle to the vertical, whose the height of cross sections and angle of installation, increase top down. At the same time, the generator is connected to a source of air supplied under pressure, and the generator is covered by side walls. The device also contains a fractions collector, installed under the nozzles [see Patent UA No. 45881 class B07B 4/02 published 15 Apr. 2002 bulletin No. 4, 2002].
In this mentioned method the separation of granular mixture into individual fractions occurs due to the difference in the ratio of their weight and the force of aerodynamic drag. This method, thanks to its peculiarities of the action mode of air jets on the particles of the mixture is more accurate and stable over time than the usual passing of the mixture through the continuous flow of air, especially when the separation of particles of irregular shape takes place. This has become possible due to the fact that the effect of the flow of the cascade of air stream jets allow multiple and different ways of impact, practically at every particle of the free-flowing granular mixture.
However, despite the advantages, this method of separation of the free-flowing granular mixture and the device for its realization have some significant drawbacks. Alternating and free mode of expiration of the cascade of air jets inevitably leads to a periodic and unstable in time and space formation in the cascade jets pressure and separation zones with occurrence of the direct and reverse currents. In the zone of reverse currents the particles of the mixture are drawn (especially light) into the motion, which is opposite to the main stream of air, that leads to a partial mixing of the already separated material with a still non separated material. The instability of this phenomenon in time, as result, leads to the opening (rupture) of the cascade of air jets in any random place, that further enhances the reverse air flow in this area and, as a consequence, intensifies mixing of the separated material with a non separated material. In addition, the opening of the cascade of the air jets contributes to the disruption of generation (cessation of the oscillatory process), that significantly reduces the quality of the separation process, and brings it closer to the quality of separation by the ordinary blowing. The mentioned disadvantages of the known method of separation are due to the imperfect construction of the device, in particular, the construction of its air jets generator.
These drawbacks are partially eliminated in other technical solutions, for example, in the described below method of separation of granular mixtures and in the device for its implementation, the essence of which consists in the following.
The method of separation of granular mixture in a flowing medium, consists of gravitational feeding of the mixture particles in a separation zone, of the aerodynamic monotonically increasing impact on the particles at the acute angle to the vertical by a cascade of flat jets, and of the extraction of finished fractions, with the aerodynamic effect being carried out in the mode of self-oscillatory motion of each jet and the entire cascade of jets at the frequency of the first harmonic of the oscillations.
The device for realizing this method of separation of granular mixture in a flowing medium contains a hopper with a vibrating chute, an air jet generator installed underneath of them, with flat nozzles located one under another and at an acute angle to the vertical, the height of the cross sections of which, the step and the installation angle of which increase from top to bottom, and the generator is connected to a source of air supplied under pressure and surrounded by sidewalls to prevent air from sucking from the environment. The device also contains a separation chamber, under which a collector of fractions is mounted, as well as each pair of adjacent nozzles is equipped with a resonance chamber, that is connected with the space between the nozzles. Resonance cameras, in turn, are equipped with a device to regulate their volume, and the ratio of the height of the nozzles' cross section to the step of their installation is in the range of 0.2-0.25, and the ratio of the extreme upper and extreme lower corners of nozzle installation is 0.65-0.75 [see Ukrainian Pat. No. 60254 for classes B07B 4/02, A01F 12/44, published Jul. 15, 2005, in the Bulletin No. 7, in 2005].
The main disadvantage of the known method of separation of the granular mixture is that it is performed using an open flowing supply system for the separation process, in particular, air stream. In the known method the air stream is sucked into the generator of the cascade jets from the environment, and then it returns to the environment after using it for separation of the free-flowing granular mixtures, however, the “exhausted” air stream returns already saturated with the ordinary dust and volatile impurities of biological origin, that automatically generates a number of additional adverse effects of the known method of separation, namely:
worsening of workers health, by causing contamination of lungs, contribution to unwanted allergic reactions (medical effect), pollution of the environment and the room in which the working device is operating (ecological effect). Thus, despite the acceptable quality of the separation process, the commercial attractiveness of the known method of separation is reduced due to the constant presence of a dense dust cloud in the operating area of the device (economic effect). It can even ignite fires that often leads to the destruction of premises, equipment and casualties among the workers due to explosion of the air-dust mixture when it reaches the critical concentration in the room. And this, in turn, forces to equip the room with a powerful ventilation system what increases the cost of the finished (separated) grain products, due to increase of the total cost of technological equipment and of energy consumption associated with this method of separation.
All mentioned disadvantages of the known method of separation of granular mixture in a flowing medium take place due to the structural imperfection of the device, with the help of which the method is implemented. In the construction of the device the node filter that cleans the air stream coming from the separation chamber from impurities and dust, forming a dangerous air-dust cloud near the device during its operation, does not exist.
However, equipping a conventional device with the node filter of any known construction automatically increases the energy consumption of the separation method, due to the corresponding increase the power of the supply drive to the generator, because such a filter element, according to its density, creates a tangible aerodynamic resistance to air stream. For this reason, equipping the known device with the node filter is non-acceptable solution of the problem of cleaning the exhausted air from the point of economic and energy indicators.
The closest in its essence and achievable effect, taken as a prototype, is a method of separation of granular mixture in a flowing medium, which is based on providing gravitational supply of the mixture's particles to a separation zone, on aerodynamic monotonously increasing impact of a cascade of flat jets on granular mixture at an acute angle to the vertical and on the extraction of the finished fractions, the lightest, solid and volatile fractions of impurities, calibrated by their size into two independent fractions, and the smallest of them, along with the major part of air stream already used for the separation returned to the drive of supplying air to the generator, in which the indicated minor fractions of solid impurities are given acceleration for the mechanical impact with the separated pieces of material, and also, the second impenetrable larger fractions of volatile impurities, with the dust and the remaining exhaust stream of air are continuously removed to the environment.
The device for implementing the above described method of separation of granular mixture in flowing medium, contains a hopper with a vibrating chute, mounted under them generator of cascade of flat jets, with flat nozzles installed in it, one under another, at an acute angle to the vertical, the height of cross sections of which, their step and installation angle, increase from the top to the bottom and which is connected with the drive of air supply under pressure to the generator that is covered by side walls, the separation chamber, under which the fractions collector is located. At the same time the outlet of the separation chamber is covered by the filtering element, made in the form of a rotating drum with a calibrating sieve on its surface, equipped externally with a cleaner of impassable solid impurities outside, wherein the internal area of the rotating drum is connected with the drive, that supplies air under pressure to the generator of the cascade flat jets (reverse path), and the cleaner is made in the form of the consecutively slotted confuser, fan and cyclone with a waste hopper installed so that the filtering element abuts the entrance of the slit of the confuser with a gap, one of the edges of which is provided with a scraper made, for example, in the form of a simple manual brush. As a version of the device, the last chute of a fractions collector that is intended to collect the non-volatile waste of the separation process and a hopper for fugitive waste which gets out from the cyclone, can be combined together into a single structure [see Ukrainian Pat. No. 96814, classes B07B 4/02, A01F 12/44, published on 12 Dec. 2011, in bull. No. 23/2011].
The main disadvantage of the known method of separation of granular mixture in flowing medium is unpredictability of the quality of the process of separation of the mixture into separate fractions. This drawback is due to lack of technical means for alignment of the air stream at the outlet of the actuator which supplies the air under pressure or in front of the generator of the cascade of air jets.
It is known that the air stream at the outlet of the actuator, in this case a centrifugal fan (although the type of the drive does not have any matter), has an excessive turbulence structure with different pressures in the section (the largest in the center of the air stream). Such unbalanced air pressure and air stream is supplied to the nozzles of the generator, and then into the separation zone.
If we use for the separation an unbalanced cascade of air jets, it will be impossible to achieve a uniform aerodynamic action on the particles of the mixture throughout the entire volume of the separation chamber.
Therefore, the separation process is uncontrolled and has fairly low quality, because the different impact of air jets on the mixture automatically sends a certain amount of granular mixture particles to the wrong chutes (trays) of the fraction collector, into which they were supposed to fall with a stable process of separation. The presence of this technological disadvantage is due to the technical (constructional) imperfections of the device—there are no technical tools to equalize the powerful air stream by pressure and laminar flow in the area between the drive of air supply and the air stream cascade generator.
The second significant disadvantage of the known method of separation of granular mixture in flowing medium is the gradual decline of the quality of separated material due to its contamination with mineral dust and small volatile fractions of impurities of biological origin. The presence of this drawback is explained as follows. The only obstacle on the way of volatile impurities is the filtering element.
However, the small volatile impurities and dust, penetrating into it, and on the reverse path coming to the drive and from it, through the generator of the cascade jets, into the zone of separation, are added to the dust and impurities entering the zone of separation with new portions of the mixture to be separated. Therefore, if dust and small volatile impurities pass through the filtering element, then there is nothing to prevent them to pass again through the same filter and pass repeatedly. So over the time, in a closed volume of the separation zone, the total amount of dust and volatile fine impurities will increase. In the end, their mass may exceed the critical point (the maximum permissible level), causing the dust with impurities to fall into a fraction collector, clogging the separated material that dramatically reduces the quality of the material. The presence of this technological disadvantage of known method is associated with technical imperfection of the used device—the device does not have technical tools for periodical removal of excess amounts of dust and volatile contaminants from the closed system of functional units of the device. Besides, the excessive amount of dust and impurities in the closed system of the device can disturb its work, and thus, disrupt the stability of the separation process of granular mixture in the flowing medium, and an excessive amount of dust, is explosive.
The next significant drawback of the known method of separation of the free-flowing granular mixture in the flowing medium is the limited scope of its application which is due to the following (in the example of crop seeds separation). Grains of the granular mixture of cereal crops have certain sizes and weights. In this method, the free-flowing granular mixture, irrespective of its kind, is supplied gravitationally to the separation zone. Moreover, the distance from the edge of vibrating chute to the first jet of air coming out of the upper nozzle of the generator of the cascade of jets, is always the same, due to the immobility of the hopper that is installed above the jets generator.
Therefore, if seeds are supplied to the separation zone, such as poppy seeds grains of which are small in size and weight, or seeds of grass crops (which tends to adhere to each other), they need to have a large kinetic energy of fall, so they can manage to delaminate during the time of free falling (this is possible if the distance between the hopper and the entrance to the separation chamber is sufficiently large). Otherwise, they will just be blown out from the separation zone by the first (upper) air stream, if the capacity of the device increases. If the small seeds are delaminated in a free flight, they are individually separated by cascade of jets into separate factions and fall into appropriate chutes of the fractions collector.
However, if other seeds are fed to the separation zone, such as corn, grains of which are large in size and weight, then they, having a large kinetic energy of falling (if the distance between the hopper and the separation chamber is significant), in the first (upper) air stream (or several upper jets), will just “slip” without separation and will not be completely divided into separate fractions by the rest air streams (the remaining jets do not have time for efficient separation of the grains into fractions because there is no sufficient number of them), and they will get into the chutes of the fractions collector without good separation into their respective fractions. Therefore, for such seeds it is necessary to reduce the kinetic energy of falling, for example, by approaching the hopper to an inlet of the separation chamber. As it was already mentioned, the presence of this shortcoming is due to the immobility of the hopper, that does not allow to adjust the distance between the vibrating chute and the first air jet, in other words, it does not allow to regulate the kinetic energy of the falling grains.
In addition, the device, in particular, its hopper, can not take into account the form of granular mixture (its roughness, humidity, ability to form arches), therefore, it cannot guarantee the stability of feeding of the mixture to the vibrating chute, what is its a significant drawback. Thus, the known method and device for its implementation are not versatile, that limits their technological capabilities.
Another disadvantage of the known method of separation is its inability to ensure continuity of the process of separation of the granular mixture, due to the fact that it is delivered to the hopper without preliminary preparation, that consists of the removal from the mixture the overly large impurities of mineral and biological origin (e.g., rocks, root systems of plants, etc.). If the large mentioned impurities fall into the separation chamber, they can damage the equipment or “drown out” some of his ladders, what will negatively affect the stability of the separation process with an unacceptable decrease of the quality of the final separated product. Consequently, the absence of a device for preliminary preparation of the granular mixture in the process of separation in this device, is its drawback that negatively affects the continuity of the process of separation of the granular mixture.
The fifth disadvantage of the known method of separation of the granular mixture in flowing medium is its insensitivity to changes of conditions from which, on many occasions, the quality of the separation process is dependent. Such conditions may include the abrupt change in the quantity (volume per unit of time) of gravitational feeding of the granular mixture in the separation zone, as well as change of parameters of electrical network, for example, voltage or current frequency. If such deviations occur, the device is unable to respond appropriately since there is no automatic change of the power of the drive that supplies the air to the generator, which is a significant drawback, because while the conditions change, the separation process will still occur according to pre-set parameters, and this will inevitably lead to the worsening of the quality of the separated final products.
The sixth disadvantage of the known method of separation of the granular mixture in the flowing medium is that it does not consider the continuously changing conditions of separation, that is explained as follows. A part of the air stream is removed outside the device, beyond the limits of the device, together with the impurities through the exhaust fan. As a result, not full air stream comes back to the reverse path, and non-static flow of air is found returned to the actuator, not in the state of co-viscous of the same pressure which was involved in the process of separation from the beginning.
Moreover, the lack of air in the reverse path gradually increases, that automatically changes the conditions of flow of the granular mixture. The absence of technical means in the device that compensate for part of the volume of the lost air is its structural disadvantage that affects the quality of the final (screened) product. In addition, in implementation of the known method, sometimes an opposite situation takes place—when the pressure in the separation zone increases and becomes higher than necessary. This situation occurs when the filtering element is clogged so that its capacity for the air returned to the reverse path is diminishes. However, the known method does not provide a means of controlling the pressure in the separation zone, for example, through the periodical automatic relief of excess pressure. Another factor in the destabilization of the separation process is the external, natural or artificial conditions that may occur unpredictably. This is the environment, in particular weather phenomena such as wind, if the device is operated outdoors or drafts—if the device is operated indoors. It is possible to protect the separation process from the influence of these negative phenomena by providing the full protection of the zone of separation from them.
But the most important factor of the noted conditions of separation is that the mentioned changes of separation conditions, can be controlled visually, because the device is made of opaque material that forces to take samples of the separated material constantly and to judge them on their quality against the changed conditions, and if necessary, to change manually the parameters of the separation process.
The seventh disadvantage of the known method of separation of the granular mixture in flowing medium is that the finished (separated) final product is removed to chutes of a fractions collector, preferably where it is reloaded into the container of unstable forms (bags or packages). Firstly, it is not convenient since the separation of the granular mixture into many fractions, the bags should be set close to each other, and in the process of filling them with grains, due to the expansion of such (unstable) type of the packaging, the bags will be adjacent to each other, so they must be somehow “pull” or “pull out” of the device, secondly, it is needed quite often to remove a fraction (or fractions), into a certain area without loading it into containers. The impossibility of withdrawal of the final product to any desired location is the significant disadvantage of the known device, due to the imperfection of the design of its fractions collector.
The eighth disadvantage of the known method of separation of the granular mixture in flowing medium is its limited functional capabilities, for example, this method cannot be applied for drying of cereal seeds. Although it is possible to change the “purge” mode of the granular mixtures to “drying”, but such drying will be prevented by some device nodes, specifically, there is no point in the filtering element that creates an obstacle to the free passage of air along the reverse path that also returns the humidified air to the initial position to the generator in the cyclone that in this case is advisable to be replaced by conventional sediment chamber fractions collector, because there is no separation of the granular mixture into the fractions necessary during its drying, while in the construction of the device, there are no tools to control humidity of the air, in terms of which the quality of the finished (dried) product can be evaluated.
The main disadvantage of the device of separation of the granular mixture in a flowing medium, which realizes the above mentioned method, is that its control panel is mounted directly on it. This limits the viewing area of the device by the operator making the job dangerous due to his constant presence near the device.
Another disadvantage of the known device for separation of the granular mixture is that it has a coherent structure that cannot be dissembled into individual units (modules). This shortcoming significantly hampers performance of maintenance work, if it is necessary to replace quickly the individual units, complicates transport to a remote distance, especially large quantities of devices to customers, to complete (create) blocks of device structure that would best meet needs of customers and resolve the necessary technological challenges.
The third disadvantage of the known device is that the actuator of air supply is rigidly connected to the electric motor, which forces it to be near the drive. Of course, this affects negatively the working conditions of the electric motor, because it is located inside the device (no cooling). It also makes difficult to substitute it with another if necessary, but more importantly, if a replaceable electric motor will have a connection unit (shaft) of another size of construction or design than provided for this type of the actuator of air supply (fan), that usually occurs in the use of imported electric motors at the place of foreign customers, so it cannot be managed to connect without any prior changes of construction of the connecting node of the fan (or electric motor), also this change of the connecting nodes is almost impossible to do in nonstationary conditions of the device usage, due to the lack of (in such conditions) necessary equipment, for example, turning, milling, drilling machines. In addition, different customers, often foreign, can have different parameters of the electrical network, for example, voltage, power phase, current frequency than the manufacturer of the devices has. Therefore, the use of external electric motor with a flexible connectivity will allow to connect it to any type of the actuator (fan) of air supply, and it can be replaced quickly into needful, without any design changes of the device units.
A number of disadvantages of the known device is associated with the imperfection of its fractions collector, including rotary shutters, the upper ends of which damages the grain material, sometimes even cut the grains. In addition, nozzles of exit chutes are fixed, that forces rearrangement of the chutes in order to change the direction of the nozzle (direct and inverse fractions) and there are no units of the device that may remove the final product for a certain distance from the device into predetermined area. Another drawback is that the fractions collector is made in the form of chutes, the design of which cannot be changed (except by rotating), for example, by volume. There is no point in such devices when the chutes are used for drying grains.
Another significant disadvantage of the known device is its limited technical capacity to move into a new technological solutions, as well as its design has no means for automatic loading of the granular mixture and discharge (unloading) of finished products, which makes its technically imperfect, since this factor requires additional service, additional labor and technical resources.
The presented critical analysis of the known technical solutions categorically assures that the disadvantages of the know methods of separation of the granular mixture in a flowing medium lies in a causal connection of the structurally deficient parts of the device, with help of which it is carried out.